1. Field of Invention
The invention relates to a fan and an impeller thereof and, in particular, to a fan and an impeller, which have multiple sets of blades.
2. Related Art
Since the present electronic products are rapidly developed towards high performance, high frequency, high speed and more compact, the generated heat of the electronic products becomes greater. However, the electronic products may unstable in the high temperature so that the reliability thereof is affected. Thus, the heat dissipation has become an important issue of the present electronic products.
The fan is a common heat dissipating device for the electronic product. As shown in FIG. 1, a conventional impeller 10 mainly includes a plurality of blades 101 and a hub 102. The blades 101 are disposed around the hub 102. The hub 102 is used for accommodating a motor (not shown), which drives the impeller 10 to rotate.
Since the need for heat dissipation is larger, the performance of the fan must be higher. In general, for increasing the airflow quantity, the size of the blades 101 is enlarged and the thickness of the blades 101 becomes thinner. To maintain the strength of the large-sized blades 101, the prior art adopts metal blades or adds a circular ring 11 for strengthening the structure of the impeller 10. Herein, the circular ring 11 is disposed around the periphery of the blades 101.
The design of the blades 101 is to make the airflow field smoother. However, when the airflow flows through the impeller 10, it will be interfered by the circular ring 11, which leads to the poor efficiency of a part of the airflow near the circular ring 11. Furthermore, the airflow may be have reflux around the impeller 10, resulting in waste of the fan power.
Therefore, it is an important subject to provide a fan and an impeller thereof, which can avoid the airflow reflux and have good airflow efficiency.